In conventional audio tape recorders, particularly those intended for recording speech, automatic recording level control has been provided to assure adequate recording level even though the speech level may be low. Provision in such conventional audio tape recorders is also present to prevent overload if the speech level becomes too high.
The automatic conventional level controls, however, do not discriminate between the speech signals and undesirable sounds which may be gathered by the microphone. The conventional automatic level controls respond, instead, to the average total sound pressure applied to the microphone.
Thus, if the speech amplitude at a distance somewhat remote from the microphone is comparable to the noise amplitude as it impinges on the microphone, the automatic control will reduce the gain to a point where the recorded speech may be unintelligible.